This invention relates to a starting fuel system for an engine and more particularly to an improved arrangement for providing starting fuel to a fuel injected two cycle crankcase compression internal combustion engine.
The advantages of two cycle internal combustion engines in providing not only simplicity but high output for a given displacement are well known. One main disadvantage to conventional two cycle crankcase compression internal combustion engines is their somewhat poor fuel efficiency and the undesirable exhaust gas emissions normally associated with such engines. To solve or minimize these problems, it has been proposed to provide direct cylinder injection for a two cycle engine. By providing direct cylinder injection, it is possible to better control the amount of fuel consumed by the engine and also to control the amount of undesirable exhaust gas constituents. However, when all of the fuel for the two cycle engine is delivered by means of a direct injection system, certain problems arise.
One specific problem is that direct injected two cycle engines do not start as well as conventional two cycle engines. During starting, even if high atomization is possible with direct injection, the fuel may not vaporize to the extent necessary to permit good starting with relatively small amounts of fuel. In addition, direct cylinder injection may, upon starting operation, give rise to a higher than desired exhaust gas emission of unburned hydrocarbons.
In addition, when all of the fuel for a two cycle engine is supplied directly to the combustion chamber, problems can occur under high speed, high load conditions. Normally a two cycle engine is at least partially cooled by the evaporation of the fuel as it flows through the crankcase and scavenge passages. When no fuel is delivered through the crankcase chamber, then overheating can occur under high load, high speed conditions.
It is, therefore, a principal object of this invention to provide an improved fuel injection system for a two cycle crankcase compression internal combustion engine.
It is a further object of this invention to provide an improved arrangement for providing starting fuel to a fuel injected engine.
It is yet another object of this invention to provide a fuel injection system for a two cycle crankcase compression internal combustion engine wherein fuel may be supplied both directly to the combustion chamber and to the engine through its induction system so as to improve starting and high speed running while maintaining all of the advantages of direct fuel injection.